MALATE UTILIZATION BY A GROUP D STREPTOCOCCUS .2. EVIDENCE FOR ALLOSTERIC INHIBITION OF AN INDUCIBLE MALATE DEHYDROGENASE (DECARBOXYLATING) BY ATP AND GLYCOLYTIC INTERMEDIATE PRODUCTS

1. 1. An inducible malate dehydrogenase (decarboxylating) (l-malate:NAD+ oxidoreductase (decarboxylating), EC 1.1.1.39) from Streptococcus faecalis was shown to be subject to a product inhibition by nucleoside triphosphates and several glycolytic intermediates. 2. 2. The glycolytic intermediate products, fructose 1,6-diphosphate, 3-phosphoglyceric acid and 6-phosphogluconate acted as competitive inhibitors for the substrate while ATP was an apparent competitive inhibitor for both substrate and cofactor. 3. 3. Kinetic and thermal inactivation studies indicated the four inhibitors could be classified as negative allosteric effectors; under appropriate conditions fructose 1,6-diphosphate and 3-phosphoglyceric acid enhanced the reaction rate of the malate dehydrogenase (decarboxylating). 4. 4. The physiological importance of the malate dehydrogenase (decarboxylating) feedback control to malate utilization by the organism is discussed. © 1969.